Heat oven to 350°F. Lightly coat 9 x 9 x 2-inch square baking pan with cooking spray.
Stir together the flour, unsweetened cocoa powder, baking soda and salt in a medium-size bowl until well mixed.
Beat together butter and sugar at high speed in large bowl until light and fluffy, about 2 minutes. Beat in vanilla.
Alternately beat in flour mixture and coffee until well blended. Pour into prepared pan.
Bake in 350°F oven for 30 to 35 minutes or until wooden pick inserted in center comes out clean. Cool in pan on wire rack 10 minutes. Unmold cake onto rack to cool.
Just before serving, beat together marshmallow cream and chocolate syrup in a bowl. Cut cake into rectangles. Spoon chocolate mixture generously over cake.